Experimental and theoretical study of the nonlinear birefringence in the formation process of vector solitons in a total polarization control ring cavity bias twist fiber

In this work, we present the numerical and experimental investigation of the polarization dynamics in a free birefringence mode-locked fiber laser. The laser includes a double-pass Erbium-doped fiber amplifier and 20-m long bi-twisted fiber at a twist rate of +/- 6 turns m(-1) to mitigate both, linear and circular birefringence effects. We found ellipticity changes due to nonlinear birefringence in the 20-m long fiber during pulse formation and propagation. In contrast with previously reported works, the inclusion of bi-twisted fiber allows investigate the nonlinear effects independently from the linear ones. The experimental behavior was confirmed by numerical simulations based on split step Fourier method showing that the polarization changes are generated since the vector soliton formation process.

Automated summary

The study investigated the polarization dynamics in a free birefringence mode-locked fiber laser through numerical and experimental methods, revealing changes in ellipticity due to nonlinear birefringence in a 20-m long bi-twisted fiber. The inclusion of bi-twisted fiber allowed for independent investigation of nonlinear effects and linear effects.